Are we there yet? Rosetta closes in on comet close encounter

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Could Rosetta unlock Earth's secrets?

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If successful, the Rosetta mission will be the first to orbit and land on a comet

Scientists hope to learn more about the composition of comets

The robotic lander Philae is due to touch down in November

Could comets have brought water to the Earth? Rosetta may help answer the question

After a 10-year chase taking it billions of miles across the solar system, the Rosetta spacecraft is homing in on its close encounter with a comet.

Pictures of the oddly-shaped rock have already been returned but on Wednesday scientists at the European Space Agency, which is leading the project, say they hope to see images from within about 75 miles as the probe carries out the last of its braking maneuvers.

If successful, the mission will notch up a series of firsts. Rosetta will be the first spacecraft to orbit a comet on its journey around the sun, and in November mission controllers aim to place the robotic lander Philae on the surface -- something that has never been done before.

Previous missions have performed comet fly-bys but Rosetta is different. This probe will follow the comet for more than a year, mapping and measuring how it changes as it is blasted by the sun's energy.

Rosetta: The comet chaser 27 photos

Rosetta: The comet chaser27 photos

Rosetta: The comet chaser – The Rosetta spacecraft snapped this wide-angle view of Comet 67P/Churyumov-Gerasimenko in September 2014. It was released January 22, 2015, by the European Space Agency. Rosetta was about 107 million miles (172 million kilometers) from Earth and about 92 million miles (148 million kilometers) from the sun when the photo was released.

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Rosetta: The comet chaser27 photos

Rosetta: The comet chaser – A camera on Rosetta took this picture of Comet 67P/Churyumov-Gerasimenko on November 22, 2014, from a distance of about 19 miles (31 kilometers). The nucleus is deliberately overexposed to reveal jets of material spewing from the comet. The 2.5-mile-wide (4-kilometer) comet has shown a big increase in the amount of water its releasing, according to NASA. The space agency says about 40 ounces (1.2 liters) of water was being sprayed into space every second at the end of August 2014.

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Rosetta: The comet chaser – Rosetta took this picture of a section of the comet's two lobes from a distance of about 5 miles (8 kilometers) on October 14, 2014.

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Rosetta: The comet chaser – The Rosetta spacecraft's Philae lander is shown sitting on Comet 67P/Churyumov-Gerasimenko after becoming the first space probe to land on a comet on November 12, 2014. The probe's harpoons failed to fire, and Philae bounced a few times. The lander was able to send back images and data for 57 hours before losing power.

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Rosetta: The comet chaser27 photos

Rosetta: The comet chaser – Rosetta's lander, Philae, wasn't able to get a good grip on the comet after it touched down. This mosaic shows Philae's movements as it bounced across the comet.

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Rosetta: The comet chaser – Philae snapped these images after landing, and mission scientists used them to create a panoramic view of the landing site. A graphic shows where the probe would be sitting in the photograph.

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Rosetta: The comet chaser27 photos

Rosetta: The comet chaser – The image of Comet 67P/Churyumov-Gerasimenko was taken by a camera on the Philae lander during its descent to the comet on November 12, 2014. The lander was about 1.9 miles (3 kilometers) from the surface at the time. Philae touched down on the comet about seven hours later.

Rosetta: The comet chaser – Rosetta's lander Philae took this parting shot of its mother ship shortly after separation on November 12, 2014, as Philae headed for a landing on Comet 67P. While Philae is the first probe to land on a comet, Rosetta is the first to rendezvous with a comet and follow it around the sun.

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Rosetta: The comet chaser – This mosaic is made of four individual images taken about 20 miles (31.8 kilometers ) from the center of the comet on November 4, 2014.

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Rosetta: The comet chaser – Rosetta took this image of comet 67P/Churyumov-Gerasimenko on September 15, 2014. The box on the right shows where the lander was expected to touch down.

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Rosetta: The comet chaser – The spacecraft sent this image as it approached the comet on August 6, 2014. From a distance of nearly 81 miles (130 kilometers), it reveals detail of the smooth region on the comet's "body" section.

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Rosetta: The comet chaser – This image, captured August 7, 2014, shows the diversity of surface structures on the comet's nucleus.

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Rosetta: The comet chaser – The comet's "head" can be seen in the left of the frame as it casts a shadow over the "body" in this image released August 6, 2014.

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Rosetta: The comet chaser – This image of the comet was taken on August 1, 2014, as Rosetta closed in its target.

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Rosetta: The comet chaser – Rosetta's mission started on March 2, 2004, when it was launched on a European Ariane 5 rocket from Kourou, French Guiana.

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Rosetta: The comet chaser27 photos

Rosetta: The comet chaser – Rosetta is named after the Rosetta Stone, the black basalt that provided the key to deciphering Egyptian hieroglyphs. Scientists think the mission will give them new clues about the origins of the solar system and life on Earth. The mission is spearheaded by the European Space Agency with key support from NASA.

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Rosetta: The comet chaser – This photo shows Rosetta being tested before it was wrapped in insulating blankets and loaded on a rocket for launch.

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Rosetta: The comet chaser – Rosetta has massive solar wings to power the spacecraft. They were unfurled and checked out at the European Space Agency's test facilities before being packed up for liftoff.

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Rosetta: The comet chaser – After its closest approach to Earth in November 2007, Rosetta captured this image of the planet.

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Rosetta: The comet chaser – Rosetta snapped this image of Earth in November 2009. The spacecraft was 393,328 miles from Earth.

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Rosetta: The comet chaser – Rosetta passed asteroid Steins in September 2008, giving scientists amazing close-ups of the asteroid's huge crater. The asteroid is about 3 miles in diameter.

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Rosetta: The comet chaser – Rosetta took this image of Mars as it looped through the solar system.

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Rosetta: The comet chaser – This image was taken by an instrument on Rosetta's Philae lander just minutes before the spacecraft made its closest approach to Mars. Part of Rosetta and its solar arrays are visible.

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Rosetta: The comet chaser – On July 10, 2010, Rosetta flew about 1,864 miles from asteroid Lutetia, which is 10 times larger than asteroid Steins.

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Rosetta: The comet chaser – Look closely at the top of this picture. See that dot? That's Saturn. Rosetta snapped the picture of asteroid Lutetia and captured Saturn in the background.

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Rosetta: The comet chaser – After taking pictures of Earth, Mars and asteroids, Rosetta was put into hibernation in May 2011 after it reached the outer part of the solar system. Mission managers woke it January 20, 2014.

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EXPAND GALLERY

Mission controllers had to use the gravity of Earth and Mars to give the probe a slingshot acceleration to meet its target on the right trajectory. Rosetta also had to be put into hibernation for more than two years to conserve power before being woken up successfully in January this year.

Scientists hope to learn more about the composition of comets and perhaps whether they brought water to the Earth or even the chemicals that make up the building blocks of life.

"It really is such a step forward to anything that has come before," project scientist Matt Taylor told CNN.

Rosetta will soon begin mapping the surface of Comet 67P/Churyumov-Gerasimenko and find out more about its gravitational pull. This will help to find a suitable landing site for Philae and allow engineers to keep Rosetta in the right orbit.

As comets approach the sun, any ice melts and is turned into an ionized gas tail. The dust produces a separate, curving tail. It's these processes that Rosetta scientists hope to be able to study from close proximity.

Taylor explained that the survey will show the team what the comet nucleus looks like now and when it gets closer to the sun.

"We'll be able to make a comparison to now, when its relatively inert, to when it's highly active ... making this measurement over a year when we're riding alongside at walking pace and observing how a comet works and interacts with the sun," he said.

"We are there for over a year to see this compete development to the extent that you may even be able to measure the decrease in the volume of the nucleus ... see how much material has left the comet."

Rosetta's target comet 67P/Churyumov-Gerasimenko is known as a short-period comet. It reappears every six years as its orbit brings it close to the sun. Halley's comet has a period of about 76 years and is not due to return close enough to Earth to be visible until 2061. Others only return after thousands of years.

Matt Taylor says it is unlikely that you will be able to see comet 67P with the naked eye but you can follow the progress of the mission on Rosetta's blog and find out more with CNN's interactive coverage.